diff --git a/core/lib/Drupal/Core/Template/AttributeString.php b/core/lib/Drupal/Core/Template/AttributeString.php
index 9776467..716ae42 100644
--- a/core/lib/Drupal/Core/Template/AttributeString.php
+++ b/core/lib/Drupal/Core/Template/AttributeString.php
@@ -29,7 +29,9 @@ class AttributeString extends AttributeValueBase {
    */
   public function __toString() {
     $this->printed = TRUE;
-    return check_plain($this->value);
-  }
-
+    $chkd = check_plain($this->value);
+    $attr = preg_replace_callback("(&[^&]+[^;];)",
+      function ($match) { return "&" . substr($match[0],5);}, $chkd);
+     return $attr;
+       }
 }